Quantum Dots

Quantum dots are nanoscale semiconductor particles that emit light at specific wavelengths when illuminated, depending on their size. In this demonstration, vials of quantum dots of different sizes are exposed to UV light. Electrons in the vials are excited to higher energy states (from the valance band to the conducting band). When the excited electron returns to the valance band, it emits a photon of energy equal to the change in electron energy. This is called photoluminescence. The color of the emitted light shifts from red to blue as the size of the quantum dots decreases, demonstrating the quantum confinement effect where the energy levels of the electrons are influenced by the size of the particles.